The present invention relates to the art of guiding tools, such as cutting tools, over a curved path with respect to a work piece.
The cutting of accurate and uniform curved surfaces is a problem which has stimulated attention from artisans over the centuries. With the advent of modern mass production techniques, however, the problem has become even more acute since the artisan may no longer cut the curved surfaces by cutting and fitting the curved surface to adjacent pieces in the final assembly of the finished product. Instead, the techniques of mass production require accuracy, uniformity and interchangeability among the pieces to be used in the various manufacturing and construction processes.
In addition to the needs of mass production, certain specialized manufacturing and construction projects also require accuracy and uniformity among the various curved parts to be used in the process. For example, in the construction of large metal tanks and vessels, the ribs on the inside of the tank or vessel must be accurate in their curvature and must be of uniform curvature and width.
Regardless of whether the materials to be cut are for use in mass production or as a part of a specialized manufacturing or construction process, accuracy, both with regard to the shape of the curve, and the smoothness of the cut, is of paramount importance.
A basic method of cutting a curved surface is to cut a template of the curve which then provides a pattern for cutting other curved pieces. The shape of the curve on the template is often physically plotted on the template before the template is cut, but the accuracy so achieved may be lost if the template is not thereafter cut with precision, if the curve is not accurately transferred from the template to the work piece, or if the cut on the work piece does not precisely follow the curve transferred to the work piece from the template.
Another method of cutting curves is to physically guide the cutting tools along a curved path. One method of guiding the cutting tool is to provide a base having a grooved track along which the tool travels as it makes the cut. While it has been known in the prior art to machine a curved track in a base material to provide such a guide, the large size of many curves makes accurate machining of such curved tracks both expensive and difficult.
Another method of guiding cutting tools is to provide a curved track along which the cutting tool may travel, which curved track is made of "lead or other soft material adapted to be easily bent or curved in the desired direction" such as that shown in U.S. Pat. No. 1,162,587 issued to Peter Eimann. It appears, however, that such curved tracks were permanently bent in the desired curved shape since it appears that the track was capable of maintaining its shape without any external restraints required to preserve the curvature of the track. Further, the accurate formation of such curved tracks undoubtedly required great care and precision. Such tracks also appear to have been cumbersome and somewhat fragile in that great care would be required to avoid distortion of the curvature of the track by rough handling on the job site. Finally, the detailed interface between the curved track and the carriage which it supported may well have required such precision in fabrication that the curved track could not easily, readily and accurately have been fabricated at the job site from readily available materials.